Storage system

ABSTRACT

A system includes: a copy processing means configured to copy a copy source file system that includes storage data and key data referring to the storage data and being unique depending on the data, from a copy source storage system storing the copy source file system into a copy destination storage system, thereby forming a copy destination file system; and an update data specifying means configured to compare the key data within the copy source file system with the key data within the copy destination file system and specify, as update data, the storage data within the copy source file system referred to by the key data within the copy source file system, the storage data not existing in the copy destination file system. The copy processing means is configured to copy the update data stored within the copy source file system into the copy destination file system.

TECHNICAL FIELD

The present invention relates to a storage system, and specifically,relates to a storage system that distributes and stores data into aplurality of storage devices.

BACKGROUND ART

In recent years, as computers have developed and become popular, variouskinds of information are put into digital data. As a device for storingsuch digital data, there is a storage device such as a magnetic tape anda magnetic disk. Because data to be stored has increased day by day andthe amount thereof has become huge, a high-capacity storage system isrequired. Moreover, it is required to keep reliability while reducingthe cost for storage devices. In addition, it is required that data canbe retrieved later with ease. As a result, such a storage system isdesired that is capable of automatically realizing increase of thestorage capacity and performance thereof, that eliminates a duplicate ofstorage to reduce the cost for storage, and that has high redundancy.

Under such circumstances, in recent years, a content address storagesystem has been developed as shown in Patent Document 1. This contentaddress storage system distributes and stores data into a plurality ofstorage devices, and specifies a storing position in which the data isstored based on a unique content address specified depending on thecontent of the data. To be specific, the content address storage systemdivides predetermined data into a plurality of fragments, adds afragment that is redundant data thereto, and stores these fragments intoa plurality of storage devices, respectively.

Later, by designating a content address, it is possible to retrievedata, that is, fragments stored in storing positions specified by thecontent address and restore the predetermined data before being dividedfrom these fragments.

Further, the content address is generated so as to be unique dependingon the content of data. Therefore, in the case of duplicated data, it ispossible to acquire data having the same content with reference to datain the same storing position. Accordingly, it is not necessary toseparately store duplicated data, and it is possible to eliminateduplicated recording and reduce the data capacity.

On the other hand, although having high redundancy as described above,the content address storage system also needs a replication of storeddata. In this case, the content address storage system executes aprocess of retrieving a file system of a copy source and copying thefile system to a file system that becomes a copy destination. Then, inthe case of having executed the copying process once, the contentaddress storage system compares the copy source file system with thecopy destination file system and specifies an update file in the copysource file system, thereby being capable of reducing time required forthe copying process.

[Patent Document 1] Japanese Unexamined Patent Application PublicationNo. JP-A 2005-235171

However, in a case that a huge amount of files are stored in a filesystem to be copied, it takes much processing and time to execute aprocess of specifying an update file updated after the previous copyingprocess. For example, in the case of specifying an update file byretrieving and comparing update time information of the respective filesstored in the copy source file system and the copy destination filesystem, respectively, it is necessary to retrieve the update timeinformation of all of the files. This causes a problem that time for thecopying process and load of the system increase and the performance ofthe system decreases.

SUMMARY

Accordingly, an object of the present invention is to provide a storagesystem that is capable of controlling time and load required for thedata copying process and inhibiting decrease of the performance of thesystem.

In order to achieve the object, a replication system of an embodiment ofthe present invention includes: a copy source storage system configuredto store a copy source file system that includes storage data and keydata referring to the storage data and being unique depending on thedata referred to thereby; and a copy destination storage systemconfigured to become a copy destination of the copy source file systemstored in the copy source storage system,

the replication system also includes: a copy processing means configuredto copy the copy source file system stored in the copy source storagesystem into the copy destination storage system, and form a copydestination file system in the copy destination storage system; and anupdate data specifying means configured to compare the key data withinthe copy source file system with the key data within the copydestination file system and specify, as update data, the storage datawithin the copy source file system referred to by the key data withinthe copy source file system, the storage data not existing in the copydestination file system, and

the copy processing means is configured to copy the update data storedwithin the copy source file system into the copy destination filesystem.

Further, a replication device of another embodiment of the presentinvention includes: a copy processing means configured to copy a copysource file system stored in a copy source storage system storing thecopy source file system that includes storage data and key datareferring to the storage data and being unique depending on the datareferred to thereby, into a copy destination storage system, and form acopy destination file system in the copy destination storage system; andan update data specifying means configured to compare the key datawithin the copy source file system with the key data within the copydestination file system and specify, as update data, the storage datawithin the copy source file system referred to by the key data withinthe copy source file system, the storage data not existing in the copydestination file system, and

the copy processing means is configured to copy the update data storedwithin the copy source file system into the copy destination filesystem.

Further, a computer program of another embodiment of the presentinvention includes instructions for causing an information processingdevice to realize: a copy processing means configured to copy a copysource file system stored in a copy source storage system storing thecopy source file system that includes storage data and key datareferring to the storage data and being unique depending on the datareferred to thereby, into a copy destination storage system, and form acopy destination file system in the copy destination storage system; andan update data specifying means configured to compare the key datawithin the copy source file system with the key data within the copydestination file system and specify, as update data, the storage datawithin the copy source file system referred to by the key data withinthe copy source file system, the storage data not existing in the copydestination file system, and

the copy processing means is configured to copy the update data storedwithin the copy source file system into the copy destination filesystem.

Further, a replication method of another embodiment of the presentinvention includes: copying a copy source file system stored in a copysource storage system storing the copy source file system that includesstorage data and key data referring to the storage data and being uniquedepending on the data referred to thereby, into a copy destinationstorage system, and forming a copy destination file system in the copydestination storage system; comparing the key data within the copysource file system with the key data within the copy destination filesystem, and specifying, as update data, the storage data within the copysource file system referred to by the key data within the copy sourcefile system, the storage data not existing in the copy destination filesystem; and copying the update data stored within the copy source filesystem into the copy destination file system.

With the configurations as described above, the present invention canrealize a storage system that controls time and load required for thedata copying process and inhibits decrease of the performance of thesystem.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration of a whole systemincluding a storage system of a first exemplary embodiment of thepresent invention;

FIG. 2 is a block diagram showing a schematic configuration of thestorage system of the first exemplary embodiment of the presentinvention;

FIG. 3 is an explanation view for explaining an aspect of a data storingprocess in the storage system disclosed in FIG. 2;

FIG. 4 is an explanation view for explaining an aspect of the datastoring process in the storage system disclosed in FIG. 2;

FIG. 5 is a view showing an aspect of storing data into a storage devicein the storage system disclosed in FIG. 2;

FIG. 6 is a function block diagram showing a configuration of thestorage system disclosed in FIG. 2;

FIG. 7 is a function block diagram showing a configuration of thestorage system disclosed in FIG. 2;

FIG. 8 is a flowchart showing an operation of the storage systemdisclosed in FIG. 2;

FIG. 9 is a flowchart showing an operation of the storage systemdisclosed in FIG. 2;

FIG. 10 is a view showing an aspect of data processing in the storagesystem disclosed in FIG. 2;

FIG. 11 is a view showing an aspect of data processing in the storagesystem disclosed in FIG. 2;

FIG. 12 is a view showing an aspect of data processing in the storagesystem disclosed in FIG. 2;

FIG. 13 is a view showing an aspect of data processing in the storagesystem disclosed in FIG. 2;

FIG. 14 is a view showing an aspect of data processing in the storagesystem disclosed in FIG. 2; and

FIG. 15 is a function block diagram showing a configuration of a storagesystem of a second exemplary embodiment of the present invention.

EXEMPLARY EMBODIMENTS First Exemplary Embodiment

A first exemplary embodiment of the present invention will be describedwith reference to FIGS. 1 to 14. FIG. 1 is a block diagram showing aconfiguration of a whole system. FIG. 2 is a block diagram showing aschematic configuration of a storage system. FIGS. 3 and 4 are viewsshowing an aspect of storage of data into the storage system. FIG. 5 isa view showing an example of metadata to be stored. FIGS. 6 and 7 areviews showing a configuration for executing replication of the storagesystem. FIGS. 8 and 9 are flowcharts each showing an operation of thestorage system. FIGS. 10 to 14 are views showing aspects of dataprocessing in the storage system.

This exemplary embodiment shows a specific example of a storage systemdisclosed in a second exemplary embodiment described later. Below, acase of configuring the storage system by connecting a plurality ofserver computers will be described. However, the storage system of thepresent invention is not limited to being configured by a plurality ofcomputers, and may be configured by one computer.

As shown in FIG. 1, a storage system of the present invention isequipped with a master storage system 10 and a replica storage system 20connected via a network N. The master storage system 10 is connected toa backup system 11 that controls a backup process via the network N. Thebackup system 11 acquires a backup target file stored in a backup targetdevice 12 connected via the network N, and requests the master storagesystem 10 to store. Thus, the master storage system 10 has a function ofstoring the backup target file requested to be stored as a backup.

Further, the storage system of the present invention has a function ofcopying data stored in the master storage system 10 (a copy sourcestorage system) into the replica storage system 20 (a copy destinationstorage system) as described above, thereby configuring a replicationsystem. The master storage system 10 and the replica storage system 20have almost the same configurations, and data stored therein are almostidentical.

As shown in FIG. 2, the master storage system 10 of this exemplaryembodiment is configured by connecting a plurality of server computers.Because the replica storage system 20 employs the same configuration asthe master storage system 10, a detailed description thereof will beomitted.

To be specific, the master storage system 10 is equipped with anaccelerator node 10A serving as a server computer that controls astoring and reproducing operation by the storage system 10, and astorage node 10B serving as a server computer equipped with a storagedevice that stores data. The number of the accelerator nodes 10A and thenumber of the storage nodes 10B are not limited to those shown in FIG.2, and the master storage system may be configured by connecting morenodes 10A and more nodes 10B.

The accelerator node 10A is equipped with a file system unit (now shown)constructed by installing an accelerator node program. This file systemunit has a function of managing backup target files acquired from thebackup system 11, data storing positions in which the data are actuallystored, and so on, so as to be retrievable later. A description of amore detailed configuration of the accelerator node 10A will be omitted.

The storage node 10B is equipped with a storage node controlling unit(not shown) and a master file system 12 shown in FIG. 5. The storagenode controlling unit is realized by installing a storage node programinto the storage node 10B.

The master file system 12 is formed in the storage device and, asdescribed later, is equipped with a metadata unit 50 that storesmetadata and a data unit 90 that stores division data configuring afile.

A basic data storing process, data retrieving process and storage datastructure in the abovementioned master storage system 10 will bedescribed with reference to FIGS. 3 to 5.

Firstly, upon acceptance of an input of backup target data A as shown byarrow Y1 in FIG. 4, the storage system divides the backup target data Ainto block data D having predetermined capacities (e.g., 64 KB) as shownin FIG. 3 and by arrow Y2 in FIG. 4. Then, based on the data content ofthe block data D, the storage system calculates a unique hash value H(content identification information) representing the data content(arrow Y3). The storage system calculates the hash value H based on thedata content of the block data D, for example, by using a preset hashfunction. This process is executed by, for example, the accelerator node10A.

Further, the master storage system 10 checks whether or not the blockdata D has already been stored in the storage devices by using the hashvalue E1 of the block data D of the backup target data A. To bespecific, the block data D having already been stored is registered inan MFI (Main Fragment Index) file in a state that the hash value H and acontent address CA representing a storing position are related.Therefore, in a case that the hash value H of the block data Dcalculated before being stored exists in the MFI file, the masterstorage system can determine that the block data D having the samecontent has already been stored (arrow Y4 in FIG. 4). In this case, themaster storage system acquires the content address CA related to thehash value H within the MFI file that coincides with the hash value H ofthe block data D before being stored, from the MFI file. Then, themaster storage system returns this content address CA as the contentaddress CA of the block data D required to be stored. Consequently, thealready stored data referred to by using this content address CA is usedas the block data D required to be stored, and it becomes unnecessary tostore the block data D required to be stored.

Further, the master storage system 10 compresses the block data Dconsidered not to have been stored yet as described above, and dividesthe data into a plurality of fragment data having predeterminedcapacities as shown by arrow Y5 in FIG. 4. For example, as denoted byreference symbols D1 to D9 in FIG. 3, the master storage system dividesthe data into nine fragment data (division data 41). Moreover, thestorage system generates redundant data so that the original block datacan be restored even if some of the fragment data obtained by divisionare lost, and adds the redundant data to the fragment data 41 obtainedby division. For example, as denoted by reference symbols D10 to D12 inFIG. 3, the storage system adds three fragment data (redundant data 42).Thus, the storage system generates a data set 40 including twelvefragment data composed of the nine division data 41 and the threeredundant data.

Further, the master storage system 10 distributes and stores thefragment data composing the data set generated as described above intostorage regions formed in the storage devices, respectively. Forexample, in a case that the twelve fragment data D1 to D12 are generatedas shown in FIG. 3, the fragment data D1 to D12 are stored into datastorage files respectively formed in the twelve storage devices,respectively (refer to arrow Y6 in FIG. 4).

Further, the master storage system 10 generates and manages a contentaddress CA, which represents the storing positions of the fragment dataD1 to D12 stored in the storage devices as described above, that is, thestoring position of the block data D to be restored from the fragmentdata D1 to D12. To be specific, the master storage system 10 generates acontent address CA by combining part of the hash value H calculatedbased on the content of the stored block data D (short hash; e.g.,beginning 8 bytes of the hash value H) with information representing alogical storing position. Then, this content address CA is returned to afile system within the master storage system 10, namely, to theaccelerator node 10A (arrow Y7 in FIG. 4). The accelerator node 10Arelates identification information such as the file name of the backuptarget data with the content address CA and manages in the file system.

In this exemplary embodiment, specifically, present time informationthat represents present time is included in the content address CA.Thus, the content address CA (key data) referring to stored fragmentdata (storage data) is set so as to be unique.

Further, the master storage system 10 relates the content address CA ofthe block data D with the hash value H of the block data D, and thestorage nodes 10B each manage in the MFI file (arrow Y8 in FIG. 4).Thus, the content address CA is related with information that specifiesthe file, the hash value H and so on, and stored into the storagedevices of the accelerator node 10A and the storage node 10B.

Furthermore, the master storage system 10 executes a control ofretrieving stored backup target data as described above. For example,when the storage system 10 accepts a retrieval request with a specificfile designated, the master storage system 10 firstly designates acontent address CA composed of short hash as part of a hash valuecorresponding to the file relating to the retrieval request andinformation of a logical position, based on the file system. Then, themaster storage system checks whether or not the content address CA isregistered in the MFI file. In a case that the content address CA is notregistered, the requested data is not stored, so that an error responseis returned.

On the other hand, in a case that the content address CA relating to theretrieval request is registered, the master storage system specifies astoring position designated by the content address CA and retrievesfragment data each stored in the specified storing position as datarequested to be retrieved. Then, the master storage system restores theblock data D from the respective fragment data retrieved in response tothe retrieval request. Moreover, a storing position management unit 25connects a plurality of restored block data D to restore as a group ofdata like the file A, and returns to the accelerator node 10A that iscontrolling the retrieval

Then, as shown in FIG. 5, the content address CA (key data) representingthe storing position of the storage data described above is stored asmetadata into the metadata unit 50 in a hierarchical structure. To bespecific, the metadata unit 50 has a root node 60, an index node 70 anda leaf node 80 that store metadata referring to data stored in a dataunit 90 and metadata referring to other metadata. The respectivemetadata stored in the root node 60, the index node 70 and the leaf node80 are newly generated or updated and stored by the storage nodecontrolling unit at the time of storing data or at any time.

Furthermore, with reference to FIG. 5, stored data stored in the dataunit 90 and the respective metadata (content addresses (key data))stored in the root node 60, the index node 70 and the leaf node 80 andrepresenting the storing positions of the stored data, which aresubjected to a storage process by the storage node controlling unit,will be described in detail.

Firstly, stored data 91, 92 and 93 stored in the data unit 90 aredivision data obtained by dividing a file that is a storage targetstored in the storage system.

Metadata 81 and 82 stored in the leaf node 80 are data representing thestoring positions of the stored data 91, 92 and so on. To be specific,as illustrated, the metadata 81 stored in the leaf node 80 has anaddress part 81 b storing a content address (CA) that is addressinformation representing the storing position of the stored data 91 orthe like, and an offset part 81 a storing position-in-file information(file offset) representing a relative position within a file beforedivision of the stored data 91 or the like.

The CA (content address) stored in the address part 81 b refers to thestored data 91 or the like stored in the data unit 90, and is uniquedata to the storing position of the stored data 91. For example, thecontent address CA is data generated so as to include part of a hashvalue generated based on the data content of stored data to be referredto and information representing physical position information. Inparticular, in this exemplary embodiment, when the stored data 91 beingreferred to is updated, present time information is included in thecontent address CA referring the stored data. Consequently, the contentaddress CA becomes more unique information depending on data beingreferred to. Moreover, the file offset stored in the offset part 81 a isdata representing a relative-position-in-file within a file beforedivision of the stored data 91 or the like referred to by thecorresponding CA.

Next, metadata 71 and 72 stored in the index node 70 will be described.The metadata 71 stored in the index node 70 is data representing astoring position of the metadata 81 or the like stored in the leaf node80. To be specific, as illustrated, the metadata 71 stored in the indexnode 70 has an address part 71 b storing a content address (CA) that isaddress information representing a storing position of the metadata 81or the like stored in the leaf node 80, and an offset part 71 a storingposition-in-file information (file offset) representing a relativeposition within a file before division of the stored data. The offsetpart and the address part are stored so as to correspond to each other.

The content address CA stored in the address part 71 b is unique data tothe storing position of the metadata 81 within the leaf node 80 beingreferred to. For example, the content address CA is data generated so asto include part of a hash value generated based on the data content ofthe metadata 81 being referred to and information representing physicalposition information.

Next, metadata 61, 62 and 63 stored in the root node 60 will bedescribed. The metadata 61 stored in the root node 60 is located on thetop of the metadata described above, and is data representing thestoring position of the metadata 71 stored in the index node 70. To bespecific, as shown in FIG. 5, the metadata 61 stored in the root node 60has an address part 61 b storing a content address (CA) that is addressinformation representing a storing position of the metadata 71 or thelike stored in the index node 70, and an offset part 61 a storingposition-in-file information (file offset) representing a relativeposition within a tile before division of stored data located at areference destination of the CA. The offset part and the address partare stored so as to correspond to each other.

The content address CA stored in the address part 61 b is unique data tothe storing position of the metadata 71 within the index node 70 beingreferred to. For example, the content address CA is data generated so asto include part of a hash value generated based on the data content ofthe metadata 71 being referred to, and information representing physicalposition information.

Further, the file offset stored in the key part is data representing arelative-position-in-file of stored data located at a referencedestination of a corresponding content address CA. In other words, thefile offset represents the order in a file before division of the storeddata 91 or the like finally specified by being referred to by themetadata 81, 82 or the like within the leaf node 80 referred to by themetadata within the index node 70 referred to by the content address CA.

The metadata denoted by reference numeral 61 is metadata correspondingto the file A. In other words, by using the stored data referred to byfollowing all of the metadata (the metadata 71, 81 and so on within theindex node 70 and the leaf node 80) referred to by the metadata 61, itis possible to configure the file A before division.

Thus, at the time of storing a file, the storage node controlling unitdivides the file and stores the division data into the data unit 90.Then, the storage node controlling unit hierarchically generates orupdates the respective metadata referring to the stored data as shown inFIG. 5. At this moment, the storage node controlling unit generates acontent address (CA) of metadata so as to refer to other existingmetadata or stored data located in lower hierarchies, thereby beingcapable of inhibiting duplicate storage of metadata and stored data.

In particular, in this exemplary embodiment, as described above, whenthe stored data 91 being referred to is updated, present timeinformation is included into the content address CA within the leaf node80 referring to this stored data. Thus, the content address CA becomesinformation that is more unique to the data being referred to. Then,based on the content address CA that is unique information, contentaddresses CA of the upper hierarchies (the index node, the root node)referring to the metadata including the content address CA that isunique information are also updated so as to include the uniqueinformation. For example, the content address CA in this exemplaryembodiment is generated so as to be unique by a unique key generationunit 139 (a unique information generating means) described later.

However, the content address CA is not limited to including present timeinformation necessarily. As described above, the content address CA mayinclude part of a hash value of data of a reference destination. Withthis, it is also possible to use the content address CA as unique keydata referring to specific data.

Further, at the time of retrieving a file, the storage node controllingunit follows the reference destinations of the respective metadata toretrieve the stored data 91 and so on being referred to, and generatesand retrieves the file. For example, at the time of retrieving the fileA when data are stored as shown in FIG. 5, the storage node controllingunit follows the metadata 61 within the root node 60 referring to thefile A, the metadata within the index node 70 referred to by themetadata 61 and the metadata within the leaf node 80, and retrieves aplurality of stored data finally referred to. Then, the storage nodecontrolling unit reproduces the file in the order represented by thefile offsets within the respective metadata.

Next, a configuration and an operation for executing replication of thestorage system will be described with reference to FIGS. 6 to 8.

Firstly, in the master storage system 10 and the replica storage system20 configuring the storage system of this exemplary embodiment, as shownin FIG. 6, the accelerator nodes 10A and 20A are respectively equippedwith replicators 11 and 21 having a function of executing replication.These replicators 11 and 21 execute a process of copying the master filesystem 12 stored in the master storage system 10, into the replicastorage system 20 in cooperation with each other.

A specific function of the storage system in order to executereplication will be described with reference to FIG. 7. The functionswill be described assuming the configuration shown in FIG. 7 is withinthe accelerator node 10A configuring the master storage system 10.However, this configuration may be installed in any computer within thestorage system.

As shown in FIG. 7, the storage system is equipped with an input device101, a copy unit 102, and a file system access unit 103. Moreover, thestorage system includes a copy source file system 200 created by thefile system access unit 103 and a copy destination file system 300.

The copy source file system 200 (a copy source FS 13) is generated bycopy of the master file system (master FS) 12 in the master storagesystem 10 at the time of replication. In a like manner, the copydestination file system 300 (a copy destination FS 23) is generated bycopy of the replica file system (replica FS) 22 in the replica storagesystem 20 at the time of replication. Thus, at the time of actualreplication, copies of the copy source file system and the copydestination file system are used. However, for the convenience ofdescription, the description will be made below assuming the master filesystem 12 is the copy source file system 200 and the replica file system22 is the copy destination file system 300.

The copy unit 102 is equipped with an update file specifying unit 121and a copy processing unit 122 as shown in FIG. 7. Moreover, the filesystem access unit 103 is equipped with a file updating unit 130, a fileattribute information updating unit 131, a file attribute informationretrieving unit 132, a file data writing-out unit 133, a file dataretrieving unit 134, a file management region retrieving unit 135, afile management region updating unit 136, a data block writing-out unit137, a data block retrieving unit 138, and a unique key generating unit139.

The copy unit 102 and the file system access unit 103 are realized byinstallation of a program into an arithmetic device of the acceleratornode 10A. The program is provided to the accelerator node 10A, forexample, in a state stored in a storage medium such as a CD-ROM.Alternatively, the program may be stored in a storage device of anotherserver computer on the network and provided to the accelerator node 10Afrom the other computer via the network.

Next, an operation of the storage system with the abovementionedconfiguration will be described with reference to a data structure viewof FIG. 8 and flowcharts of FIGS. 9 and 10. Firstly, an operation whendata within the master file system 12 stored in the master storagesystem 10, namely, data within the copy source file system 200 isupdated will be described. To be specific, an operation when data(storage data) referred to by a file attribute part 262 stored in thecopy source file system 200 is updated will be described.

Firstly, when the file system access unit 103 accepts a request toupdate a file (step S1), the file updating unit 130 receives a filenumber and update file data. Then, the file updating unit 130 passes thefile number and the update file data to the file data writing-out unit133, whereby the update file data is written out (step S2).

Subsequently, after the update file data is written out, the fileupdating unit 130 passes the file number to the file attributeinformation retrieving unit 132, and searches for file attribute partkey information 252. After searching for the file attribute part keyinformation 252, the file updating unit 130 passes the file attributepart key information 252 to the data block retrieving unit 138, therebyretrieving the file attribute part 262.

Subsequently, the file updating unit 130 sets present time informationrepresenting present time as file update time information stored in theretrieved file attribute part 262 (step S3). Consequently, the fileattribute part 262 referring to the update file data becomes data (keydata) that is unique to the update file data. In other words, in thiscase, the file updating unit 130 functions as a unique informationgenerating means configured to include the data (key data) unique to theupdate file data into the file attribute part 262 referring to theupdate file data.

Then, the file updating unit 130 passes the file number and the fileattribute part 262 to the file attribute information updating unit 131.Upon acceptance, the file attribute information updating unit 131 passesthe file attribute part 262 to the data block writing-out unit 137.Then, the data block writing-out unit 137 writes out the file attributepart 262 (step S4).

Subsequently, the data block writing-out unit 137 acquires fileattribute part key information that is generated by the unique keygenerating unit 139 and is unique to the file attribute part 262, andreturns to the file attribute information updating unit 131. In otherwords, when the file attribute part 262 being referred to changes, theunique key generating unit 139 (a unique information generating means)generates unique file attribute part key information (key data)referring to the file attribute part 262 (step S5). Then, the fileattribute information updating unit 131 stores the file attribute partkey information returned from the data block writing-out unit 137 intothe file attribute part key information 252 corresponding to the filenumber in a file management block 241 (step S6).

Subsequently, in accordance with the change of the file attribute partkey information 252 in the file management block 241, a unique key (keydata) of the file management block 241 is generated by using the uniquekey generating unit 139 (step S7). Then, the unique key of the filemanagement block 241 generated by the unique key generating unit 139 isstored into file management block key information 231 in a filemanagement information part 221 (step S8).

Subsequently, in accordance with the change of the file management blockkey information 231, a new unique key (key data) of the file managementinformation part 221 is generated by using the unique key generatingunit 139 (step S9). Then, the generated unique key of the filemanagement information part 221 is stored into file managementinformation part key information 211 (step S10).

Data unique to data of a reference destination such as present timeinformation and a unique key is a content address referring to updatefile data or other metadata, or data included in a content address.

For example, a file system before changed shown in FIG. 11A and a filesystem after changed shown in FIG. 11B will be considered. It is assumedthat “Data” denoted by reference symbol D1 of FIG. 11B is updated fromthe file system of FIG. 11A. The value of a unique content address CA*(C1) referring to the Data (D1) is changed. In accordance with this, thecontent of metadata M1 including the content address CA* (C1) is alsochanged, and therefore, the value of the content address CA* (C2) uniqueto the metadata MI and referring to the metadata M1 is changed.

Since metadata M2 including the content address CA* (C2) is alsochanged, the value of the content address CA* (C3) unique to themetadata M2 and referring to the metadata M2 is changed. Since metadataM3 including the content address CA* (C3) is also changed, the value ofthe content address CA* (C4) unique to the metadata M3 and referring tothe metadata M3 is changed. Since metadata M4 including the contentaddress CA* (C4) is also changed, the value of the content address CA*(C5) unique to the metadata M4 and referring to the metadata M4 ischanged. Then, the content of metadata M5 including the content address(C5) is also changed.

Thus, when data stored in the storage system is updated, a contentaddress is successively changed as shown by arrow Y100 of FIG. 11B Inother words, in order from a content address referring to the updatedata located in a lower hierarchy to a content address located in anupper hierarchy referring to the metadata including the content address,the order of the content addresses is changed.

Next, replication in the master storage system 10 and the replicastorage system 20, namely, the process of copying the copy source filesystem 200 will be described. It is assumed that, previously, the copysource file system 200 is replicated from the master storage system 10to the replica file system 20 and a copy source file system that is thesame file system as the copy source file system 200 is stored in thereplica storage system 20.

In the copying process after that, firstly, the update file specifyingunit 121 (an update data specifying means) specifies a file updatedafter the previous copying process. After that, the copy processing unit122 (a copy processing means) copies the update file having beenspecified and metadata. Below, a specific description will be made withreference to FIG. 10.

Firstly, upon acceptance of a copying request by input from the inputdevice 101 (step S21), the copy unit 102 passes information specifyingthe copy source file system 200 and the copy destination file system 300to the update file specifying unit 121.

Subsequently, the update file specifying unit 121 causes the filemanagement region retrieving unit 135 of the file system access unit 103to retrieve a file system management region 201 of the copy source filesystem 200 and a file system management region 301 of the copydestination file system 300. Subsequently, the update file specifyingunit 121 compares the file management information part key information211 of the file system management region 201 with file managementinformation part key information 311 of the file system managementregion 301 (step S22).

At this moment, in a case that the two file management information partkey information coincide with each other (Yes at step S23), it isdetermined that there is no updated file, and the update file specifyingunit 121 ends the process.

On the other hand, in a case that the two file management informationpart key information do not coincide (No at step S23), which means thereis an updated file, the update file specifying unit 21 specifies theupdate file. To be specific, the update file specifying unit 121 passesthe file management information part key information 211 to the datablock retrieving unit 138, and retrieves the file management informationpart 221 referred to by the file management information part keyinformation 211. Then, file management block key information of the filemanagement information part 221 and file management block keyinformation of the file management information part 321 within the copydestination file system 300 are compared (step S24). After that, basedon the result of the comparison, different file management block keyinformation 22 is specified. Here, it is assumed that the filemanagement block key information 231 and the file management block keyinformation 331 are different.

Subsequently, file attribute part key information 251 to 253 within thefile management block 241 and file attribute part key information 351 to353 within the file management block 341 referred to by the differentfile management block key information 231 and 331, respectively, arecompared (step S25). To be specific, the file management block keyinformation 231 is passed to the data block retrieving unit 138, and thefile management block 241 is retrieved. On the other hand, the filemanagement block key information 331 is passed to the data blockretrieving unit 138, and the file management block 341 is retrieved. Thefile attribute part key information included in the retrieved filemanagement block 241 and the file attribute part key informationincluded in the retrieved file management block 341 are compared,whereby different file attribute part key information is specified (stepS26). Here, it is assumed that the file attribute part key information252 and the file attribute part key information 352 are different. Then,a file represented by the file attribute part key information 252 as thedifferent information is specified as an updated file (step S27).

After that, the copy unit 102 receives update file information from theupdate file specifying unit 121 and passes the update file informationto the copy processing unit 122, thereby executing a copying process. Atthis moment, the copy unit 102 copies the update file having beenspecified, metadata that refers to the update file, and metadata of anupper hierarchy referring to the abovementioned metadata into the copydestination file system 300. Thus, it is possible to copy only data inthe copy source file system 200 updated from data in the copydestination file system 300 into the replica storage system 20.

Next, examples of the abovementioned copying process will be describedwith reference to FIGS. 12 to 14. In the respective examples shown inthe drawings, the copy destination file system 300 is shown on the leftside, and the copy source file system 200 is shown on the right side.That is to say, the drawings each show a state that data in the copysource file system 200 has been updated from the copy destination filesystem 300. In these drawings, it is assumed that storage target data isstored in a part denoted by “Inode.”

In the beginning, in the example of FIG. 12, it is assumed that datastored in “Inode” denoted by reference symbol D11 has been updated.Firstly, when content addresses CA included in metadata located in theroot nodes of the highest hierarchy are compared, the content addressCA* denoted by reference symbol C13 within the copy source file system200 is different from the content address CA within the copy destinationfile system 300 (refer to reference numeral (1)). In other words, thecontent address CA* denoted by reference symbol C13 within the copysource file system 200 does not exist in the copy destination filesystem 300. Therefore, metadata in the index node of a lower hierarchyreferred to by the content address CA* denoted by reference symbol C13is checked.

Subsequently, when content addresses CA located in the index nodes arecompared, the content address CA* denoted by reference symbol C12 withinthe copy source file system 200 is different from the content address CAwithin the copy destination file system 300 (refer to reference numeral(2)). In other words, the content address CA* denoted by referencesymbol C12 does not exist in the copy destination file system 300.Therefore, metadata in the leaf node of a lower hierarchy referred to bythe content address CM denoted by reference symbol C12 is checked.

Subsequently, when content addresses CA located in the leaf nodes arecompared, the content address CA* denoted by reference symbol C11 withinthe copy source file system 200 is different from the content address CAwithin the copy destination file system 300 (refer to reference numeral(3)). In other words, the content address CA* denoted by referencesymbol C11 does not exist in the copy destination file system 300.Therefore, the data stored in the Inode denoted by reference symbol D11referred to by the content address CA* denoted by reference symbol C11is specified as update data.

After that, the data specified as the update data within the copy sourcefile system 200 and the metadata having been followed are copied intothe copy destination file system 300.

Thus, in the present invention, by comparing metadata within the copysource file system with metadata within the copy destination filesystem, respectively, from the highest hierarchy and following differentcontent addresses, it is possible to specify data having been updated.Therefore, there is no need to compare all of the data within therespective file systems, and it is possible to easily and speedilyspecify update data by comparing metadata that refer to storage data. Asa result, it is possible to control time and load required for the datacopying process, and it is possible to inhibit decrease of theperformance of the system.

Next, in the example of FIG. 13, it is assumed that data stored in“Inode” denoted by reference symbol D21 has been updated and thehierarchies of metadata have increased. Firstly, when content addressesCA included in metadata located in the root nodes of the highesthierarchy are compared, the content addresses CA* denoted by referencesymbols C23 and C24 within the copy source file system 200 are differentfrom the content addresses CA within the copy destination file system300 (refer to reference numeral (11)). In other words, the contentaddresses CA* denoted by reference symbols C23 and C24 within the copysource file system 200 do not exist in the copy destination file system300. Therefore, metadata in the index nodes of a lower hierarchyreferred to by the content addresses CA* denoted by reference symbolsC23 and C24 are checked.

Subsequently, when content addresses CA located in the index nodes arecompared, the content address CA* denoted by reference symbol C22 withinthe copy source file system 200 is different from the content address CAwithin the copy destination file system 300 (refer to reference numeral(12)). In other words, the content address CA* denoted by referencesymbol C22 does not exist in the copy destination file system 300.Therefore, metadata in the leaf node of a lower hierarchy referred to bythe content address CA* denoted by reference symbol C22 refers ischecked.

Subsequently, when content addresses CA located in the leaf nodes arecompared, the content address CA* denoted by reference symbol C21 withinthe copy source file system 200 is different from the content address CAwithin the copy destination file system 300 (refer to reference numeral(13)). In other words, the content address CA* denoted by referencesymbol C21 does not exist in the copy destination file system 300.Therefore, the data stored in the Inode denoted by reference symbol D21referred to by the content address CA* denoted by reference symbol C21is specified as update data.

After that, the data specified as the update data within the copy sourcefile system 200 and the metadata having been followed are copied intothe copy destination file system 300.

Next, in the example of FIG. 14, it is assumed that data stored in“Inode” denoted by reference symbols D31 and D32 have been updated.Firstly, when content addresses CA included in metadata located in theroot nodes of the highest hierarchy are compared, the content addressCA* denoted by reference symbol C34 within the copy source file system200 is different from the content address CA within the copy destinationfile system 300 (refer to reference numeral (21)). In other words, thecontent address CA* denoted by reference symbol C34 does not exist inthe copy destination file system 300. Therefore, metadata in the indexnode of a lower hierarchy referred to by the content address CA* denotedby reference symbol C34 is checked.

Subsequently, when content addresses CA located in the index nodes arecompared, the content address CA* denoted by reference symbol C33 withinthe copy source file system 200 is different from the content address CAwithin the copy destination file system 300 (refer to reference numeral(22)). In other words, the content address CA* denoted by referencesymbol C33 does not exist in the copy destination file system 300.Therefore, metadata in the leaf node of a lower hierarchy referred to bythe content address CA* denoted by reference symbol C33 is checked.

Subsequently, when content addresses CA located in the leaf nodes arecompared, the content addresses CA* denoted by reference symbols C31 andC32 within the copy source file system 200 are different from thecontent addresses CA within the copy destination file system 300 (referto reference numeral (23)). In other words, the content addresses CA*denoted by reference symbols C31 and C32 do not exist in the copydestination file system 300. Therefore, the data stored in the Inodedenoted by reference symbols D31 and D32 referred to by the contentaddresses CA* denoted by reference symbols C31 and C32 are specified asupdate data.

After that, the data specified as update data within the copy sourcefile system 200 and the metadata having been followed are copied intothe copy destination file system 300. At this moment, the update datahaving been specified, the metadata that includes the content addressesreferring to the update data, and the metadata of the higher hierarchyreferring to the abovementioned metadata are copied into the copydestination file system 300. In other words, only data within the copysource file system 200 having been changed is copied into the copydestination file system 300.

Second Exemplary Embodiment

Next, a second exemplary embodiment of the present invention will bedescribed with reference to FIG. 15. FIG. 15 is a function block diagramshowing a configuration of a storage system of this exemplaryembodiment. In this exemplary embodiment, the storage system will beschematically described.

As shown in FIG. 15, a storage system of this exemplary embodimentincludes: a copy source storage system I configured to store a copysource file system 2 that includes storage data and key data referringto the storage data and being unique depending on the data referred tothereby; and a copy destination storage system 3 configured to become acopy destination of the copy source file system stored in the copysource storage system.

Then, the storage system also includes: a copy processing means 5configured to copy the copy source file system 2 stored in the copysource storage system 1 into the copy destination storage system 3, andform a copy destination file system 4 in the copy destination storagesystem 3; and an update data specifying means 6 configured to comparethe key data within the copy source file system 2 with the key datawithin the copy destination file system 4 and specify, as update data,the storage data within the copy source file system 2 referred to by thekey data within the copy source file system 2, the storage data notexisting in the copy destination file system 4.

Furthermore, the copy processing means 5 is configured to copy theupdate data stored within the copy source file system 2 into the copydestination file system 4.

In FIG. 15, the copy processing means 5 and the update data specifyingmeans 6 are installed in a replication device 7 separately, but may beinstalled in the copy source storage system I and/or the copydestination storage system 3.

According to the storage system configured as described above, the copysource storage system stores storage data and key data referring to thestorage data, which form the copy source file system. By copying thiscopy source file system into the copy destination storage system, a copyfile system having the same content is formed within the copydestination storage system. After that, when update data is storedwithin the copy source file system, key data referring to this updatedata is generated or updated so as to include information unique to theupdate data.

Then, after that, at the time of copying the copy source file systeminto the copy destination storage system, a process of updating only adifference updated in the copy source file system is executed. To bespecific, firstly, the key data within the copy source file system iscompared with the key data within the copy destination file system. In acase that the respective key data coincide, it is determined that thereis no update data, and the copying process is stopped. On the otherhand, in a case that the key data is different, storage data referred toby the different key data in the copy source file system is specified asupdate data. After that, the specified update data is copied.

Thus, according to the present invention, there is no need to compareall of the storage data of the copy source file system and the copydestination file system, and it is possible to specify storage datahaving been updated by comparing key data referring to the storage data.Therefore, it is possible to control time and load required for the datacopying process, and it is possible to inhibit decrease of theperformance of the system.

Further, in the replication system described above, there are datareferring to the storage data and data referring to metadata includingone or plural other key data, as the key data, and the key data form ahierarchical structure. Then, the update data specifying means isconfigured to, in a case that the key data within the copy source filesystem that does not exist in the copy destination file system refers tothe metadata as a result of comparison of the key data, compare the keydata included in the metadata as a comparison target with the key datawithin the copy destination file system.

Further, in the replication system described above, the update dataspecifying means is configured to compare the key data and follow areference destination of the key data within the copy source file systemthat does not exist in the copy destination file system, therebyspecifying the update data.

Further, in the replication system described above, the update dataspecifying means is configured to compare the key data in order oflocation from a higher hierarchy to a lower hierarchy and follow areference destination of the key data.

Thus, in the case of a hierarchical structure in which metadataincluding key data referring to storage data is refers to by other keydata, it is possible to speedily specify update data by following keydata within the copy source file system that does not exist in the copydestination file system.

Further, in the replication system described above, the copy processingmeans is configured to copy update data stored in the copy source filesystem and specified by the update data specifying means, and the keydata considered by the update data specifying means not to exist withinthe copy destination file system, into the copy destination file system.

Further, in the replication system described above, the copy processingmeans is configured to copy update data stored in the copy source filesystem and specified by the update data specifying means, the key dataconsidered by the update data specifying means not to exist within thecopy destination file system, and the metadata including the key data,into the copy destination file system.

Furthermore, in the replication system described above includes a uniqueinformation generating means configured to generate unique informationdepending on data referred to by the key data and to include theinformation into the key data.

Then, in the replication system described above, the unique informationgenerating means is configured to, when the data referred to by the keydata changes by storage of the update data into the copy source filesystem, generate unique information depending on the data and includethe information into the key data referring to the data.

Further, another exemplary embodiment of the present invention is theabovementioned replication device including: a copy processing meansconfigured to copy a copy source file system stored in a copy sourcestorage system storing the copy source file system that includes storagedata and key data referring to the storage data and being uniquedepending on the data referred to thereby, into a copy destinationstorage system, and form a copy destination file system in the copydestination storage system; and an update data specifying meansconfigured to compare the key data within the copy source file systemwith the key data within the copy destination tile system and specify,as update data, the storage data within the copy source file systemreferred to by the key data within the copy source file system, thestorage data not existing in the copy destination file system, and

the copy processing means is configured to copy the update data storedwithin the copy source file system into the copy destination filesystem.

Further, in the replication device described above: as the key data,there are data referring to the storage data and data referring tometadata including one or plural other key data, and the key data form ahierarchical structure; and the update data specifying means isconfigured to, in a case that the key data within the copy source filesystem that does not exist in the copy destination file system refers tothe metadata as a result of comparison of the key data, compare the keydata included in the metadata as a comparison target with the key datawithin the copy destination file system.

Further, the aforementioned replication system or replication device canbe realized by installing a computer program into an informationprocessing device. To be specific, a computer program of anotherexemplary embodiment of the present invention includes instructions forcausing an information processing device to realize: a copy processingmeans configured to copy a copy source file system stored in a copysource storage system storing the copy source file system that includesstorage data and key data referring to the storage data and being uniquedepending on the data referred to thereby, into a copy destinationstorage system, and form a copy destination file system in the copydestination storage system; and an update data specifying meansconfigured to compare the key data within the copy source file systemwith the key data within the copy destination file system and specify,as update data, the storage data within the copy source file systemreferred to by the key data within the copy source file system, thestorage data not existing in the copy destination file system.

Then, the copy processing means is configured to copy the update datastored within the copy source file system into the copy destination filesystem.

Further, in the computer program described above, in a case that thereare data referring to the storage data and data referring to metadataincluding one or plural other key data, as the key data, and the keydata form a hierarchical structure, the update data specifying means isconfigured to, in a case that the key data within the copy source filesystem that does not exist in the copy destination file system refers tothe metadata as a result of comparison of the key data, compare the keydata included in the metadata as a comparison target with the key datawithin the copy destination file system.

Further, a replication method of another exemplary embodiment of thepresent invention executed by operation of the aforementionedreplication system includes: copying a copy source file system stored ina copy source storage system storing the copy source file system thatincludes storage data and key data referring to the storage data andbeing unique depending on the data referred to thereby, into a copydestination storage system, and forming a copy destination file systemin the copy destination storage system; comparing the key data withinthe copy source file system with the key data within the copydestination file system, and specifying, as update data, the storagedata within the copy source file system referred to by the key datawithin the copy source file system, the storage data not existing in thecopy destination file system: and copying the update data stored withinthe copy source file system into the copy destination file system.

Further, in the replication method described above, in a case that thereare data referring to the storage data and data referring to metadataincluding one or plural other key data, as the key data, and the keydata form a hierarchical structure, the update data specifying means isconfigured to, in a case that the key data within the copy source filesystem that does not exist in the copy destination file system refers tothe metadata as a result of comparison of the key data, compare the keydata included in the metadata as a comparison target with the key datawithin the copy destination file system.

Inventions of a replication device, a computer program and a replicationmethod having the abovementioned configurations have like actions as theabovementioned replication system, and therefore, can achieve the objectof the present invention mentioned above.

Although the present invention has been described with reference to therespective exemplary embodiments described above, the present inventionis not limited to the abovementioned exemplary embodiments. Theconfiguration and details of the present invention can be altered withinthe scope of the present invention in various manners that can beunderstood by those skilled in the art.

The present invention is based upon and claims the benefit of priorityfrom Japanese patent application No. 2009-041894, filed on Feb. 25,2009, the disclosure of which is incorporated herein in its entirety byreference.

INDUSTRIAL APPLICABILITY

The present invention can be utilized for a system configured byconnecting a plurality of storage systems and configured to executereplication between the storage systems, and has industrialapplicability.

DESCRIPTION OF REFERENCE NUMERALS

-   -   1 copy source storage system    -   2 copy source file system    -   3 copy destination storage system    -   4 copy destination file system    -   5 copy processing means    -   6 update data specifying unit    -   7 a replication device    -   10 master storage system    -   10A accelerator system    -   10B storage node    -   11 master replicator    -   12 master file system    -   13 copy source file system    -   20 replica storage system    -   21 replica replicator    -   22 replica file system    -   23 copy destination file system    -   31 backup system    -   32 backup target device    -   101 input device    -   102 copy unit    -   103 file system access unit    -   121 update file specifying unit    -   122 copy processing unit    -   130 file updating unit    -   131 file attribute information updating unit    -   132 file attribute information retrieving agent    -   133 file data writing-out unit    -   134 file data retrieving unit    -   135 file management region retrieving unit    -   136 file management region updating unit    -   137 data block writing-out unit    -   138 data block retrieving unit    -   139 unique key generating unit    -   201, 301 file system management region    -   211, 311 file management information part key information    -   221, 321 file management block key information    -   231, 232, 331, 332 file management block key information    -   241, 242, 341, 342 file management block    -   251,252,253,351,352,361 file attribute part key information    -   261, 263, 361, 362, 363 file attribute part    -   200 copy source file system    -   300 copy source file system

1. A replication system comprising: a copy source storage systemconfigured to store a copy source file system that includes storage dataand key data referring to the storage data and being unique depending onthe data referred to thereby; and a copy destination storage systemconfigured to become a copy destination of the copy source file systemstored in the copy source storage system, the replication system alsocomprising: a copy processing unit configured to copy the copy sourcefile system stored in the copy source storage system into the copydestination storage system, and form a copy destination file system inthe copy destination storage system; and an update data specifying unitconfigured to compare the key data within the copy source file systemwith the key data within the copy destination file system and specify,as update data, the storage data within the copy source file systemreferred to by the key data within the copy source file system, thestorage data not existing in the copy destination file system, whereinthe copy processing unit is configured to copy the update data storedwithin the copy source file system into the copy destination filesystem.
 2. The replication system according to claim 1, wherein: as thekey data, there are data referring to the storage data and datareferring to metadata including one or plural other key data, and thekey data form a hierarchical structure; and the update data specifyingunit is configured to, in a case that the key data within the copysource file system that does not exist in the copy destination filesystem refers to the metadata as a result of comparison of the key data,compare the key data included in the metadata as a comparison targetwith the key data within the copy destination file system.
 3. Thereplication system according to claim 2, wherein the update dataspecifying unit is configured to compare the key data and follow areference destination of the key data within the copy source file systemthat does not exist in the copy destination file system, therebyspecifying the update data.
 4. The replication system according to claim3, wherein the update data specifying unit is configured to compare thekey data in order of location from a higher hierarchy to a lowerhierarchy and follow a reference destination of the key data.
 5. Thereplication system according to claim 1, wherein the copy processingunit is configured to copy update data stored in the copy source filesystem and specified by the update data specifying unit, and the keydata considered by the update data specifying unit not to exist withinthe copy destination file system, into the copy destination file system.6. The replication system according to claim 2, wherein the copyprocessing unit is configured to copy update data stored in the copysource file system and specified by the update data specifying unit, thekey data considered by the update data specifying unit not to existwithin the copy destination file system, and the metadata including thekey data, into the copy destination file system.
 7. The replicationsystem according to claim 1, comprising a unique information generatingunit configured to generate unique information depending on datareferred to by the key data and to include the information into the keydata.
 8. The replication system according to claim 7, wherein the uniqueinformation generating unit is configured to, when the data referred toby the key data changes by storage of the update data into the copysource file system, generate unique information depending on the dataand include the information into the key data referring to the data. 9.A replication device comprising: a copy processing unit configured tocopy a copy source file system stored in a copy source storage systemstoring the copy source file system that includes storage data and keydata referring to the storage data and being unique depending on thedata referred to thereby, into a copy destination storage system, andform a copy destination file system in the copy destination storagesystem; and an update data specifying unit configured to compare the keydata within the copy source file system with the key data within thecopy destination file system and specify, as update data, the storagedata within the copy source file system referred to by the key datawithin the copy source file system, the storage data not existing in thecopy destination file system, wherein the copy processing unit isconfigured to copy the update data stored within the copy source filesystem into the copy destination file system.
 10. The replication deviceaccording to claim 9 as the key data, there are data referring to thestorage data and data referring to metadata including one or pluralother key data, and the key data form a hierarchical structure; and theupdate data specifying unit is configured to, in a case that the keydata within the copy source file system that does not exist in the copydestination file system refers to the metadata as a result of comparisonof the key data, compare the key data included in the metadata as acomparison target with the key data within the copy destination filesystem.
 11. (canceled)
 12. (canceled)
 13. A replication methodcomprising: copying a copy source file system stored in a copy sourcestorage system storing the copy source file system that includes storagedata and key data referring to the storage data and being uniquedepending on the data referred to thereby, into a copy destinationstorage system, and forming a copy destination file system in the copydestination storage system; comparing the key data within the copysource file system with the key data within the copy destination filesystem, and specifying, as update data, the storage data within the copysource file system referred to by the key data within the copy sourcefile system, the storage data not existing in the copy destination filesystem; and copying the update data stored within the copy source filesystem into the copy destination file system.
 14. The replication methodaccording to claim 13, wherein: in a case that, as the key data, thereare data referring to the storage data and data referring to metadataincluding one or plural other key data, and the key data form ahierarchical structure, when the key data within the copy source filesystem that does not exist in the copy destination file system refers tothe metadata as a result of comparison of the key data at the time ofspecification of the update data, comparing the key data included in themetadata as a comparison target with the key data within the copydestination file system.